Iron-containing fuel additive for reducing particulates generated during combustion

ABSTRACT

The burn properties of hydrocarbon fuels are improved by incorporating bimetallic fuel additives. The fuel additives include oil-soluble iron as a primary metal component and an oil-soluble platinum-group metal as a secondary metal component. The concentration of the platinum-group metal in the fuel additive is significantly less (e.g., an order of magnitude less) than the concentration of iron. The minute amount of platinum-group metal in combination with 1 to 100 ppm iron synergistically improves smoke point and/or utilizes less iron to achieve the same improvement in smoke point as compared to iron-based fuel additives without a platinum-group metal. The additives can also include one or more oil-soluble metal compound including an alkali metal, alkaline earth metal, lanthanide metal, actinide metal, or base transition metal such as manganese.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention relates to additives for liquid fuels. More particularly, the invention relates to oil-soluble, iron-based fuel additives that include a precious metal to reduce the smoke produced when the fuel is burned in an engine.

2. Related Technology

The combustion of hydrocarbon fuels can produce incomplete and/or undesirable products such as carbon monoxide, nitrous oxides (NO_(x)), unburned hydrocarbons, and particulates. For example, particulates generated during the combustion or pyrolysis of diesel fuels typically have inorganic ash (due to engine wear particles and combustion products of lubricant oil additives), sulfuric acid (due to sulfur in diesel fuel), and hydrocarbons from incomplete fuel combustion. The hydrocarbons are typically further divided into SOF (solvent organic fraction, i.e., material extractable in, for example, CH₂Cl₂) and a hydrocarbonaceous soot.

The emission of smoke from diesel engines and jet turbines is a well-known problem. In addition to being unsightly, such emissions contain particulates and unburned hydrocarbons which are understood to represent a hazard to health. In particular, unburned hydrocarbons emitted into the atmosphere are irritant astringent materials. Further, in a problem recently highlighted for diesel fuels, emissions of particulate matter of less than 10 micrometers (microns) are claimed to be the cause of many deaths. It is suspected that these smaller particles penetrate deeper into the lungs and adhere to the mucocilliary system. The mucocilliary system is thought to have evolved to cope with airborne dusts and pollens, but does not cope well with smaller particles, especially those of less than 2.5 μm in diameter.

In addition to health concerns, smoke emissions can also be a problem for military aircraft. There are many weapons guidance systems that detect particulates in the aircraft exhaust and use the detection as a way of tracking and/or finding the aircraft. Reducing or eliminating smoke emissions from aircraft can therefore provide a level of protection against these types of weapons systems.

Diesel engines and jet engines are especially prone to emitting high levels of small sized soot particulates when the engine is highly loaded, worn or badly maintained. Even when the engine is run at partial load and well maintained, there is still a significant amount of particulate emissions that are normally invisible to the naked eye.

A number of ways are being examined to enable diesel and jet engines to run cleaner. One approach is to design the engine and/or combustion chamber to have improved combustion efficiency. However, improvements in engine design can be expensive, complex, and generally cannot be easily retrofitted in to existing engines. Furthermore, engine modifications to reduce particulate emissions can result in lower power output and reduced efficiency, which is undesirable.

Another solution for reducing particulate emissions in combustion engines is to add a fuel additive that catalyzes the complete combustion of the fuel. Many different metals have been mixed with liquid fuels and tested in combustion engines, boilers, and combustion turbines. Examples of metals that have been used in various fuel additives include iron, manganese, copper, alkali metals, alkaline earth metals, platinum, and rare earth elements such as cerium and lanthanum. Most fuel additives using these and other catalysts reduce smoke emissions by no more than 50% and typically require metal concentrations in the fuel of at least 50 ppm on a weight/weight.

The use of an iron catalyst to reduce smoke emissions is of great interest because iron based additives have the potential to be economical and effective. One disadvantage of existing iron-based catalysts is the large amount of metal that must be used to achieve a desired smoke point reduction. The large quantities of iron in the fuel can cause an iron coating on the metal surfaces of the engine. Residual iron can change the dynamic behavior of engine and/or require frequent engine cleaning.

BRIEF SUMMARY OF THE INVENTION

This invention relates to fuel additives that include two or more different oil-soluble, organometallic compounds for reducing smoke and particulate emissions in the exhaust of combustion engines. The fuel additives include an oil-soluble iron compound as a primary metal component and a transition group metal as a secondary metal component. Transition group metals include base transition metals, platinum group metals, rare earth metals, lanthanum series metals, and actinide series metals. The combination of iron and at least one other transition metal have been found to reduce particulates in exhaust, increase the research octane number (“RON”) of the fuel, and/or otherwise improve the combustion performance of the fuel mixture. Optionally, an oil-soluble alkaline earth metals or can also be included in the fuel additive.

The iron metal component in combination with the at least one other transition metal synergistically reduces the generation of smoke and/or particulates during combustion of the fuel. According to one embodiment, the at least one other transition metal comprises at least platinum group metal (e.g., platinum, palladium, or iridium). Compared to known fuel additives, the combination of iron and the at least one other transition metal provides the same or better smoke reduction with lower concentrations of iron and while using relatively little platinum-group metal. According to another embodiment, the at least one other transition metal comprises manganese, which also helps reduce the amount of iron. Achieving a desired reduction in smoke with reduced concentrations of iron is advantageous because it reduces the amount of residual iron that can potentially coat engine parts. Thus, engines burning fuel mixtures according to the invention require less maintenance and/or have greater longevity compared to engines burning fuel additives with higher concentrations of iron.

Examples of suitable oil-soluble iron compounds that can be used in the fuel additives of the invention include iron naphthanate and iron 2-ethyl hexanoate. In one embodiment, the oil-soluble iron compound is included in the fuel mixtures of the invention at a concentration in a range from about 1 ppm to about 100 ppm of iron metal, more preferably about 2 ppm to about 50 ppm, most preferably from about 5 to about 30 ppm of iron metal. Unless otherwise specified, the term “ppm” shall refer to a mass/mass ratio.

The platinum-group metal compound typically includes one or more of Ir, Pt, or Pd in oil-soluble form. The platinum-group metal can be included in the fuel mixture at a much lower concentration than that of the iron component. In one embodiment, the concentration of platinum-group metal in the fuel mixture is in a range from about 0.01 ppm to about 10 ppm of metal, more preferably from about 0.1 ppm to about 5 ppm, and most preferably in a range from about 0.2 ppm to about 3 ppm.

An examples of a base transition metal that has been found to work well in combination with iron to synergistically improve burn catalyst includes manganese. In one embodiment, the base transition metal compound is included in the fuel mixtures of the invention at a concentration in a range from about 1 ppm to about 100 ppm, more preferably about 2 ppm to about 50 ppm, most preferably from about 5 to about 30 ppm. Typically, the other base transition metal will be included in an amount that is less than that of iron.

Optionally, the fuel additive or fuel mixture can include one or more additional oil-soluble metal components such as one or more alkaline earth metals, alkali metals, rare earth metals, lanthanide series metals, or actinide series metals. The additional metal component is typically added in a concentration in a range from about 1 ppm to about 100 ppm.

During combustion of the fuel mixture, the oil-soluble metal compounds decompose in-situ to form metal or metal oxide catalysts. The metallic catalyst formed in-situ catalyzes combustion of the fuel, thereby increasing the burning efficiency and reducing smoke and particulate emissions. The fuel additives of the invention can also increases the Research Octane Number (RON) of the liquid fuel.

These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims as set forth hereinafter.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present invention is directed to fuel additives that improve the burn properties of hydrocarbon fuels incorporating the fuel additives. The fuel additives include iron as a primary metal component and another transition metal, such as one or more of a platinum-group metal or a base transition metal (e.g., manganese) as a secondary metal component. The concentration of the platinum-group metal in the fuel additive is significantly less (e.g., an order of magnitude less) than the concentration of iron. The minute amount of platinum-group metal in combination with 1 to 100 ppm iron synergistically improves smoke point and/or utilizes less iron to achieve the same improvement in smoke point as compared to iron-based fuel additives without a platinum-group metal. The use of other transition metals, such as manganese, also greatly improves burn catalysis over the use of iron alone.

For purposes of the present invention, the term “oil-soluble” compound refers to compounds that can be dissolved or dispersed in a hydrocarbon fuel.

The fuel additives of the invention are mixed with a liquid hydrocarbon to produce a fuel mixture having improved burn properties. Metals included in the fuel additives are (i) oil-soluble iron, (ii) another oil soluble transition metal such as a platinum-group metal or base transition metal, (iii) optionally an additional oil-soluble metal such as an alkaline earth metal, an alkali metal, or an additional base transition metal, and (iv) optionally a solvent in which the oil-soluble metals are dissolved.

The primary metal component of the fuel additive of the invention is an oil-soluble iron compound. Any iron compound can be used so long as it can be dissolved or dispersed in the selected liquid hydrocarbon. The oil-soluble iron compounds are typically organometallic complexes of iron. Examples of oil-soluble iron complexes include iron naphthanate, iron carboxylate and iron β-diketonate complexes, over-based iron soaps (carboxylate or sulfonate), ferrocene, iron succinates, and iron picrate. Additional examples of suitable oil-soluble iron compounds are described in U.S. Pat. No. 6,986,327 to May, which is incorporated herein by reference.

In one embodiment, the iron-containing compound is preferably an iron carboxylate. Iron carboxylates in combination with a platinum-group compound have been found to have superior particulate reduction while also improving RON. Examples include, but are not limited to iron salts of butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, 2-ethyl butanoic acid, 2-methyl pentanoic acid, 2-ethyl hexanoic acid, and the like. Alternatively, in one embodiment, the iron compound can be iron naphthanate.

The platinum-group metal compound can be any oil-soluble compound of Pt, Pd, or Ir, including organometallic complexes of Pt, Pd, or Ir. Examples of suitable oil-soluble platinum-group metal compounds include 1,5-cyclooctadiene platinum diphenyl (platinum COD), platinum group metal acetylacetonates, platinum group metal dibenzylidene acetonates, and fatty acid soaps of tetrainine platinum metal complexes, e.g., tetramine platinum oleate. In the foregoing examples, platinum can be substituted with Pd or Ir. Acetonates and alkyl carboxylic acids, (i.e., fatty acid soaps) are preferred. Alkyl carboxylic acids are particularly preferred for their oil solubility, cost, and performance.

An example of a suitable base transition compound is an oil-soluble manganese. Additional metals include oil-soluble compounds of alkali metals, alkaline earth metals, base transition metals (other than iron), lanthanides, and the like. Examples of suitable alkaline earth metals include oil-soluble compounds of barium, magnesium, and calcium. An example of a suitable lanthanide compound is an oil-soluble cerium. The oil-soluble metals can be provided as metal complexes of butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, 2-ethyl butanoic acid, 2-methyl pentanoic acid, 2-ethyl hexanoic acid, or the like.

The fuel additive can be added to any liquid fuel so long as the components of the fuel additive alone or in combination are soluble or dispersible in the liquid hydrocarbon. Examples of suitable liquid hydrocarbons include diesel fuel, jet fuel, gasoline, biodiesel, and the like. Particulate reduction using the fuel additives of the invention can be particularly beneficial when used in diesel fuel or jet fuel.

The oil-soluble metals are mixed together and/or mixed with a liquid fuel in a desired ratio of iron to platinum-group metal and optionally a desired ratio of iron to additional metals. In one embodiment the ratio of iron to platinum group metal is in a range from about 10,000 to 1 to about 1:10, more preferably 1:10,000 to about 1:100, and most preferably in a range from 1:10,000 to 1:1,000. In an alternative embodiment, the iron concentration is at least 500 times greater than the platinum group metal concentration, more preferably greater than 1000 times, and most preferably greater than 5000 times the concentration of the platinum group metal. In the case were manganese is used instead of the platinum group metal, it is typically included in an amount that is less than the amount of iron, as measured in ppm. In the case where a platinum group metal is used, the amount of iron can be reduced, and the amount of manganese, if used, can either be less or exceed that of iron.

In one embodiment, the oil-soluble metal compounds can be mixed together to form a concentrated fuel additive having the desired ratios of metals. In this embodiment, the oil-soluble metals can be dissolved in one another or can be dissolved in a suitable solvent. Examples of solvents suitable for making concentrated fuel additives include mineral oil.

In an alternative embodiment, one or more individual components of the additive can be separately mixed into the liquid fuel. In this embodiment, the components are added to the liquid fuel so as to achieve the desired ratio of oil-soluble metals.

The concentrated fuel additive or the individual metal components of the additive are added to a liquid fuel to form a fuel mixture having a desired concentration of oil-soluble metal components. In one embodiment, the concentration of the oil-soluble iron compound in the liquid fuel is in a range from about 1 ppm to about 100 ppm of iron, more preferably from about 2 ppm to about 50 ppm, and most preferably from about 5 ppm to about 30 ppm (mass/mass). The concentration of the iron compound is selected in combination with the concentration of the platinum-group compound, the need to reduce particulate emissions, and the need to minimize residual iron on engine parts.

The concentration of the oil-soluble platinum-group metal compound in the fuel mixture can be in a range from about 0.01 ppm to about 10 ppm of metal, more preferably from about 0.1 ppm to about 5 ppm, and most preferably in a range from about 0.2 ppm to about 3 ppm. The concentration of the platinum-group metal compound is selected so as to maximize the synergistic benefits of the platinum-group metal and iron combination. The platinum-group metal compound is included in sufficient concentration to achieve a desired reduction in exhaust particulates using reduced concentrations of iron while minimizing the use of the platinum-group metal, since the platinum-group metal is relatively expensive.

The concentration of the other transition metal will typically depend on the particular transition metal that is included. In one embodiment, the other transition metal compound is included in the fuel mixture at a concentration in a range from about 1 ppm to about 100 ppm of metal, and more preferably in a range from about 5 to about 50 ppm.

The concentration of the optional additional oil-soluble metal compound will typically depend on the particular additional metal that is included. In one embodiment, the additional metal compound is included in the fuel mixture at a concentration in a range from about 1 ppm to about 100 ppm of metal, and more preferably in a range from about 5 to about 50 ppm.

The fuel additive and liquid hydrocarbon can be mixed just before use or can be pre-mixed and stored. If the fuel mixture is to be stored, the fuel additive and liquid hydrocarbon are typically selected such that the fuel additive is relatively stable in the liquid hydrocarbon. The fuel additives can include detergents or other chemicals that facilitate mixing and/or dispersing the fuel additive in the liquid fuel and/or enhance the stability of the fuel additive in the liquid hydrocarbon.

The fuel mixtures incorporating the fuel additives of the invention can be used in any combustion engine that is prone to producing particulates during combustion. The fuel mixtures can be used in turbine engines, spark ignited engines, compression ignited engines, and the like. The fuel mixtures can be advantageous for medium speed (450 to 1,000 rpm) and high speed (greater than 1,000 rpm) engines. The fuel additives of the invention have been found to work particularly well with jet fuels (i.e., kerosene) and in jet engines. Reducing particulates in the exhaust of jets (e.g., fighter jets) is beneficial for avoiding tracking by weapon systems, in addition to reducing harmful pollutants.

EXAMPLES

The following examples provide formulas for making fuel mixtures that include bimetallic oil-soluble metal additives and the use of these fuel mixtures in a combustion engine. Smoke tests were carried out by following ASTM D1322-97: Standard Test Method of Smoke Point of Kerosene and Aviation Turbine Fuel. The smoke point is the maximum height, in millimeters, of a smokeless flame of fuel burned in a wick-fed lamp of specified design. A high smoke point indicates a fuel of low smoke producing tendency. The baseline test result for aviation fuel JP8 is 25.0 mm.

Example 1

Example describes a fuel mixture with a an iron additive and a manganese additive. 833 grams of iron naphthanate (80% in mineral spirits, containing 12 wt % Fe) and 500 grams of magnesium 2-ethyl hexonate (containing 6 wt % Mg) were mixed firstly. The mixture was then added to aviation fuel JP8 to form 1,000 kg of test fuel. The smoke test result is 28.0 mm.

Example 2

Example 2 describes a fuel mixture with a platinum additive, an iron additive, and a manganese additive. 2.05 grams of platinum acetyl acetonate (containing 48.8 wt % Pt), 833 grams of iron naphthanate (80% in mineral spirits, containing 12 wt % Fe) and 250 grams of magnesium 2-ethyl hexanoate (containing 8 wt % Mg) were mixed by adding 500 ml of toluene. The mixture was finally added to aviation fuel JP8 to form 1,000 kg of test fuel. The smoke test result is 28.5 mm.

Example 3

Example 3 describes a fuel mixture with a palladium additive and an iron additive. 8.67 g of palladium acetyl acetonate (containing 34.6 wt % Pd), 417 grams of iron naphthanate (80% in mineral spirits, containing 12 wt % Fe) and 250 grams of magnesium 2-ethyl hexanoate (containing 8 wt % Mg) were mixed by adding 500 ml of toluene. The mixture was finally added to aviation fuel JP8 to form 1,000 kg of test fuel. The smoke test result is 28.0 mm.

Example 4

Example 4 describes a fuel mixture with an iridium additive, an iron additive and a magnesium additive. 7.80 g of iridium acetyl acetonate (containing 38.5 wt % Ir), 417 grams of iron naphthanate (80% in mineral spirits, containing 12 wt % Fe) and 250 grams of magnesium 2-ethyl hexanoate (containing 8 wt % Mg) were mixed by adding 500 ml of toluene. The mixture was finally added to aviation fuel JP8 to form 1,000 kg of test fuel. The smoke test result is 29.0 mm.

Example 5

Example 5 describes a fuel mixture with a palladium additive, an iron additive, a cerium additive, and a manganese additive. 2.89 g of palladium acetyl acetonate (containing 34.6 wt % Pd), 417 grams of iron naphthanate (80% in mineral spirits, containing 12 wt % Fe), 500 grams of manganese 2-ethyl hexanoate (containing 6 wt % Mn) and 167 grams of cerium 2-ethyl hexanoate (49% in 2-ethylhexanoic acid, containing 12 wt % Ce) were mixed by adding 500 ml of toluene. The mixture was finally added to aviation fuel JP8 to form 1,000 kg of test fuel. The smoke test result is 29.0 mm.

The smoke test results indicate that substantial reduction in smoke can be achieved using very low amounts of precious metal. In addition, good results are achieved using acetonates and fatty acid soaps to achieve oil solubility with the catalytic metals. 

1. A fuel mixture suitable for use in an engine, comprising: a liquid hydrocarbon fuel; and a fuel additive dissolved in the liquid hydrocarbon fuel, the fuel additive comprising: at least one oil-soluble iron compound present in the hydrocarbon in a range from about 1 ppm to about 100 ppm; and at least one other oil-soluble transition metal compound present in the hydrocarbon in an amount less than about 100 ppm.
 2. A fuel mixture as in claim 1, in which the hydrocarbon fuel is selected from the group consisting of diesel fuel, jet fuel, gasoline, and biodiesel.
 3. A fuel mixture as in claim 1, in which the oil-soluble iron compound is present in the hydrocarbon in a range from about 2 ppm to about 50 ppm.
 4. A fuel mixture as in claim 1, in which the oil-soluble iron compound is present in the hydrocarbon in a range from about 5 ppm to about 30 ppm.
 5. A fuel mixture as in claim 1, in which the at least one other oil-soluble transition metal compound comprises an oil-soluble platinum-group metal compound selected from the group of platinum compounds, palladium compounds, iridium compounds, and mixtures thereof.
 6. A fuel mixture as in claim 5, in which the oil-soluble platinum-group compound is present in the hydrocarbon in a range from about 0.01 ppm to about 10 ppm.
 7. A fuel mixture as in claim 5, in which the oil-soluble platinum-group compound is present in the hydrocarbon in a range from about 0.1 ppm to about 5 ppm.
 8. A fuel mixture as in claim 5, in which the oil-soluble platinum-group compound is present in the hydrocarbon in a range from about 0.2 ppm to about 3 ppm.
 9. A fuel mixture as in claim 5, in which the oil-soluble platinum-group compound is a organometallic complex of diphenyl acetylacetonate, dibenzylidene acetonates, a fatty acid soap, or combination thereof.
 10. A fuel mixture as in claim 1, in which the at least one other oil-soluble transition metal compound comprises manganese.
 11. A fuel mixture as in claim 1, further comprising at least one additional oil-soluble metal compound selected from the group of alkaline earth metal compounds, alkali metal compounds, rare earth metal compounds, lanthanum series metal compounds, actinide series metal compounds, and mixtures thereof.
 12. A fuel mixture as in claim 1, in which the fuel additive consists essentially of the iron compound and at least one of a manganese compound or a platinum group metal compound, and optionally at least one of an alkaline earth metal compound or a lanthanide series metal compound.
 13. A fuel mixture as in claim 1, in which the oil-soluble iron compound and the at least one other transition metal compound are metal salts of an organic molecule having from 2 to 18 carbon atoms.
 14. A fuel mixture as in claim 1, in which the oil-soluble iron compound and the at least one other transition metal compound are metal salts of at least one of butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, 2-ethyl butanoic acid, 2-methyl pentaoic acid, naphthenoic acid, acetyl acetonate, or 2-ethyl hexanoic acid.
 15. An oil soluble fuel additive for mixing with a liquid hydrocarbon fuel for reducing smoke during combustion of the hydrocarbon fuel, the additive comprising: an oil-based solvent; an oil-soluble iron compound dissolved in the solvent; at least one other oil-soluble transition metal compound dissolved in the solvent selected from the group of platinum-group metal compounds, manganese, cerium, and mixtures thereof; and optionally, an additional metal compound dissolved in the solvent, the additional metal compound comprising a metal selected from the group consisting of an alkaline earth metal, a rare earth metal, a lanthanum series metal, or an actinide series metal.
 16. An additive as in claim 15, wherein the at least one other oil-soluble transition metal compound comprises an oil-soluble platinum-group metal compound selected from platinum compounds, palladium compounds, iridium compounds, and mixtures thereof, wherein the molar ratio of the iron compound to the platinum-group compound is in a range from about 1:10,000 to about 1:10.
 17. An additive as in claim 12, in which the solvent is mineral oil.
 18. An additive as in claim 12, in which the oil-soluble iron compound is in a concentration from about 0.01% to about 1% by weight of the fuel additive.
 19. A liquid fuel suitable for use in a jet turbine engine, comprising: a jet-fuel-grade kerosene; and a fuel additive dissolved in the kerosene, the fuel additive comprising: an oil-soluble iron compound present in the hydrocarbon in a range from about 1 ppm to about 50 ppm; an oil-soluble platinum-group compound selected from the group of Pt compounds, Pd compounds, Ir compounds, and mixtures thereof, the platinum-group compound being present in the liquid fuel in a range from about 0.01 ppm to about 10 ppm; and at least one of an oil-soluble manganese compound or a magnesium compound present in the liquid hydrocarbon in a range from about 1 ppm to about 100 ppm.
 20. A liquid fuel as in claim 19, in which the oil-soluble iron compound, the platinum-group compound, and the optional additional metal compound are metal salt of an organic molecule having between 2 and 18 carbon atoms.
 21. A liquid fuel as in claim 19, in which the oil-soluble iron compound and the optional additional metal compound are metal salts of butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, 2-ethyl butanoic acid, 2-methyl pentaoic acid, naphthenoic acid, acetyl acetonate, or 2-ethyl hexanoic acid.
 22. A liquid fuel suitable for use in a jet turbine engine, comprising: a jet-fuel-grade kerosene; and a fuel additive dissolved in the kerosene, the fuel additive consisting essentially of: an oil-soluble iron compound present in the hydrocarbon in a range from about 1 ppm to about 50 ppm; an oil-soluble manganese compound present in the liquid hydrocarbon in a range from about 1 ppm to about 100 ppm; and optionally, at least one of an oil-soluble platinum-group compound, an alkaline earth metal compound, or cerium. 